Guided Wave Long Range Ultrasonic Testing

We offer Guided Wave testing (GWT),which is one of latest methods in the field of non-destructive evaluation. It is also known as Guided Wave Ultrasonic Testing (GWUT) or Long Range Ultrasonic Testing (LRUT).

The method employs mechanical stress waves that propagate along an elongated structure while guided by its boundaries. It uses low frequency guided ultrasonic waves to inspect tens of meters of pipe from a single remote location. This allows the waves to travel a long distance with little loss in energy.

The ability of this system to send waves along the length of the pipe means that difficult to inspect areas, such as road crossings, can be interrogated from a remote and easily accessible location. The inspection can usually be performed while the pipe is in service. Main application is for rapid screening of long lengths of pipe to detect external or internal corrosion as well as axial and circumferential cracking. It can be used in difficult to access tubular and piping systems such as insulated pipes in refineries and platforms, offshore pipeline risers and caissons, above ground or burried flowlines and many more.

In Guided Wave Testing of pipelines, an array of low frequency transducers is attached around the circumference of the pipe to generate an axially symmetric wave that propagate along the pipe in both the forward and backward directions of the transducer array. The equipment operates in a pulse-echo configuration where the array of transducers is used for both the excitation and detection of the signals.

At location where there is a change of cross-section or a change in local stiffness of the pipe, an echo is generated. Based on the arrival time of the echoes, and the predicted speed of the wave mode at a particular frequency, the distance of a feature in relation to the position of the transducer array can be accurately calculated. GWT uses a system of distance amplitude curves (DAC) to correct for attenuation and amplitude drops when estimating the cross-section change (CSC) from a reflection at a certain distance. The DACs are usually calibrated against a series of echoes with known signal amplitude such as weld echoes.